The Sages teach that a person earns immense reward through the proper observance of the mitzvah of tefillin. The Almighty declares through the prophet Yeshayahu,אד-ני עליהם יחיו  — “When God is upon them — they shall live” (Yeshayahu 38:16). Meaning, people who carry the Name of God upon their bodies by wearing tefillin are blessed with long life. [1] As the Yafeh Le’lev explains, the organs that play the most vital roles in sustaining a person are the brain and heart, and thus by wearing tefillin near these organs, one earns long life. Indeed, the story is told of the great Kabbalist Rabbenu Yosef Gikatilla (Spain, 13th century) who fell gravely ill, and, while he was semiconscious, he beheld two people weighing his merits against his sins, and they were found to be equal. Rabbi Yosef immediately asked for his tefillin and put them on. At that very moment, when the merit of wearing tefillin were placed on the scale, he began recovering from his illness, as the mitzvah of tefillin prolongs a person’s life.[2] The merit of this mitzvah also guarantees a person a share in the World to Come, and grants him protection from the fires of Gehinnom and forgiveness for all his sins.[3]

However, as the Kaf Ha’hayim notes, this reward hinges on the individual’s compliance with the laws governing conduct while wearing tefillin, which forbid engaging in idle or frivolous talk or performing mundane activities while wearing tefillin.

If a person does not wear tefillin due to laziness, an unwillingness to take time away from his professional pursuits, other financial concerns, or distaste for the tefillin themselves, he is classified under the category of פושעי ישראל בגופן — “Jews who sin with their bodies.” This applies even if a person neglects to wear tefillin only on occasion, and even if he neglected this mitzvah on only a single day (unless, of course, he could not wear tefillin due to circumstances beyond his control). Furthermore, the Gemara establishes[4] that failure to wear tefillin constitutes a violation of eight Biblical commands. As mentioned earlier, the Torah introduces this mitzvah in four different contexts, and thus by neglecting the tefillin shel yad and tefillin shel rosh, one is in violation of eight commands — four regarding the shel yad, and four regarding the shel rosh.

This should serve as a warning to those who wear their tefillin incorrectly, such as people who place the tefillin shel rosh on their foreheads (rather than on the top of the head). One who does not place his tefillin on the correct place on his head and on his arm is considered as not having donned tefillin at all, and is thus included under the category of פושעי ישראל בגופן 

Given the immense importance of this mitzvah and the gravity of its neglect, a person must ensure to purchase the parchment for his tefillin from a reliable, scholarly, reputable and God-fearing sofer(scribe). The straps and tefillin boxes, too, should be obtained from a reliable individual who can be trusted to prepare the straps in full accordance with Halachah. One who wears tefillin that were not produced in accordance with all relevant halachic details does not fulfill the obligation of tefillin, and all the berachot he recites when donning the tefillin are deemed berachot le’vatalah — berachot recited in vain. People exercise such meticulous care when purchasing furniture and appliances to ensure that they are in working order and of the highest quality. All the more so, it behooves one to purchase a beautiful pair of tefillin.5 One thereby fulfills the obligation of hiddur mitzvah — beautifying the mitzvah, as the Sages infer from the verse (Shemot 15:2),זה אלי ואנוהו  (“This is my God and I shall glorify Him”)